How to replace the camera glass?

The safest way is to disassemble the phone and push it out from the inside. Plenty of unauthorized repair shops can do this and shouldn’t charge you more than about $20usd. Make sure you do your research before taking it anywhere. I was horrified at how poorly everyone was trained when I regrettably worked for iFixandrepair. Talk to the owner and ask to speak with the technician that will be working on your phone. Ask them if it’s okay to watch. Most trustworthy and respectable places should have no problem asnwering your questions and allowing you to watch them fix your phone if they aren’t too busy.